The monsoon of 2025 left a path of devastation. The mountains of the Western Himalayas have crumbled into rivers of mud, causing huge ecological and economic losses. These floods have severed lives and livelihood in the affected areas. Entire communities have been swept away These flash floods were because of regular cloudburst in upper region of Himalaya.
Cloudburst, an Ecological Disaster
A cloudburst qualifies as an ecological disaster due to its sudden, intense rainfall—typically over 100 mm per hour in a small area—that trigger cascading environmental disruptions like flash floods, landslides, and soil erosion.
Cloudbursts saturate slopes, causing landslides and mudflows that bury forests, uproot trees, and destroy alpine meadows and medicinal plants. They also lead to riverbank erosion, land subsidence, and shifts in river courses, which degrade arable land, disrupt water regimes, and threaten biodiversity including endemic species like Himalayan monal and snow leopards.
Notable Examples in India
- 2013 Kedarnath, Uttarakhand: Triggered massive flash floods, causing severe soil erosion and vegetation loss.
- Recent Uttarakhand and Himachal incidents (2024-2025): Destroyed habitats, increased human-wildlife conflicts, and damaged ecosystem services like carbon sequestration.
In the Indian subcontinent, cloudbursts are common during the southwest monsoon (June-August), especially in Himalayan states like Himachal Pradesh, Uttarakhand, and Jammu & Kashmir, when monsoon clouds from the Bay of Bengal or Arabian Sea interact with terrain. Climate change exacerbates their frequency by increasing atmospheric moisture capacity.
Primary Reasons of Cloud burst
The primary reasons for cloud bursts in the northwestern region of India during this rainy season are:
- Interaction of warm, moisture-laden monsoon winds with cold mountainous air — This is a common cause of cloud bursts in the Himalayan region including northwestern India. When warm monsoon air from the Bay of Bengal or Arabian Sea rises over the cold Himalayas, it rapidly cools and condenses, leading to intense, localized rainfall over a short duration. This orographic lifting effect is amplified by steep terrain in areas like Jammu & Kashmir, Himachal Pradesh, and Uttarakhand.
| Catastrophic Interplay |
| Confluence of monsoon trough, low pressure areas, and associated cyclonic circulation from Bay of Bengal, western disturbances, Arbian Sea winds have led excess rainfall in northern and north-wet region. Basically, these cloud bursts were because of the collusion both wind one coming from mediterranean and Arabian sea and the second one the monsoon coming from Bay of Bengal. Confluence of western disturbance and monsoon came as a climate emergency. |
- Increased frequency and intensity of western disturbances — This monsoon season witnessed an unusually high number of western disturbances, which are extra-tropical storms originating from the Mediterranean and moving eastward. These disturbances bring cold air that clashes with warm monsoon air, causing extreme rainfall and cloud bursts, especially in the western Himalayas. The interaction of western disturbances with the monsoon rain system was unusually strong this season, intensified by jet stream shifts due to global warming
| Western Disturbances and its Potential Vorticity? |
| Western disturbances are extra – tropical storms in the middle to upper layers of the troposphere that usually originate around Mediterranean region. Typically, these western disturbances use to come in the month December to February in 3/ 4 number. However, from June to 7th September this year, India could see 19 western disturbances. This time the nature of these western disturbances was mix of many flavours. It was identified as cold-core, low- pressure systems in upper layer of troposphere that get cut-off, from the Arctic jet stream and move towards lower latitude. The total western disturbances accounted for 10% which, after collision with monsoon in the North- west and Northern region of the country, culminated into cloud bursting and heavy rains. |
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- Influence of shifts in jet streams — The subtropical jet stream, a fast air current in the upper atmosphere, generally moves west to east but due to warming, it has become more erratic and shifted southwards this season. This shift led to the merging of cooler air from the jet stream with moisture-laden monsoon air at lower altitudes in the northwestern region, triggering cloudbursts.
| Sub-Tropical Jet Stream and Its Impact? |
| The STJ is a fast-moving air current flowing west to east at high altitudes (12-14 km) typically between 25° to 35° N latitude. During winter, it flows south of the Himalayas, while in summer, it shifts northwards closer to the northern edge of the Himalayas and Tibetan Plateau. The northward shift of the STJ in early June creates an upper-air space vacated by the jet stream, enabling the ascent of warm, moist monsoon air and formation of low pressure at the surface. This triggers the burst or onset of the monsoon rains. The presence or absence of the STJ also influences large-scale atmospheric stability. When the jet stream moves southwards during the withdrawal phase (September-October), it induces subsidence (downward air movement) that suppresses convection, reduces rainfall, and helps replace moist monsoon winds with dry winds, thus driving the monsoon retreat. The position and intensity of the STJ affect Western Disturbances and upper-level divergence, which impact cloud formation and precipitation patterns in northwestern India, sometimes contributing to extreme events like cloud bursts. Climate change and warming are causing the subtropical jet stream to become more erratic in its shifts and intensity, which contributes to unusual rainfall variability and extreme weather events during the monsoon. In essence, the subtropical jet stream governs the timing of monsoon onset by moving northwards in summer, promotes monsoon withdrawal by moving southwards later in the season, and influences the stability and rainfall distribution over India during the season. |
- Climate change effects — Rising global temperatures increase atmospheric moisture capacity, intensifying cloudbursts and their frequency, especially in monsoon-prone Himalayan regions. Human activities like deforestation, unregulated construction, and hydropower projects exacerbate ecological damage by destabilizing slopes and altering natural drainage.
In summary, the cloud bursts in northwestern India this rainy season are caused by a complex interplay of warm, moist monsoon air and cold air from western disturbances and mountain ranges, exacerbated by changes in jet stream patterns and intensified by climate change-driven increases in atmospheric moisture. These factors jointly produce conditions conducive to extremely heavy, sudden rainfall events in this region.